A population-based study of the prevalence of COVID-19 infection in Espírito Santo, Brazil: methodology and results of the first stage
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Abstract
BACKGROUND
COVID-19 is affecting almost the entire world, causing more than four hundred thousand deaths and undermining the health care systems, as much as the economy, of the afflicted countries. The strategies for prevention depend on largely lacking information, as infection prevalence and virus pathogenicity. This study aimed to determine the prevalence, the pathogenicity, and the speed of infection spreading in a large population in Brazil.
MATERIALS AND METHODS
This is a serial cross-sectional study designed on a population basis and structured over houses as the sampling units. The sampling consisted of four visits at 15 days intervals in randomly selected census-designated sectors of the State major municipalities (reference municipalities) and two visits at 30 days intervals in smaller municipalities of the same regions of those of reference. At each visit, the investigators sampled houses and sampled one individual in each house for data collection. After the informed consent, the investigators performed a rapid antibody detection test (Celer Technology, Inc) and applied a questionnaire containing clinical and demographic questions.
RESULTS
From May 13th to 15th, the investigators performed 6,393 rapid tests in 4,612 individuals of the reference municipalities, 1,163 individuals of the smaller municipalities, and 166 contacts of the positive individuals. Ninety-seven dwellers were positive in the reference municipalities, giving a prevalence of 2.1% (CI 95%: 1.67-2.52%). In the smaller municipalities, the figure was 0.26% (CI 95%: 0.05%-0.75%) (three positives). There was an association of the positive result with female sex (p = 0.013) and houses with five dwellers or more (p = 0.003). Seventy-eight positive individuals reported symptoms in the previous 15 days (80.4%), being anosmia (45.4%), cough (40.2%), and myalgia (38.1%) the more frequent. About one-third of them reported fever (28.9%).
CONCLUSIONS
The results reveal a still small prevalence of infection in the study area, despite the significant number of sick people overloading the health system. The figures indicate an important underreporting in the area and a frequency that still can grow, making necessary public health actions for the containment of the transmission.
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SciScore for 10.1101/2020.06.13.20130559: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement Consent: Data collection: After the informed consent, the volunteers participated in an interview that provided information regarding the following variables: sex, age, education level of the person with the highest level of education in the house, and self-referred skin colour.
IRB: This study had the approval of the Committee on Ethics of Research on Human Beings of the University Hospital Cassiano Antonio de Moraes of the Federal University of Espírito Santo, under the insertion number CCAE 31417020.3.0000.5064 and the approval number 4.009.337.Randomization The samples were multiples of 40 because it was the number established for sampling in each one of the … SciScore for 10.1101/2020.06.13.20130559: (What is this?)
Please note, not all rigor criteria are appropriate for all manuscripts.
Table 1: Rigor
Institutional Review Board Statement Consent: Data collection: After the informed consent, the volunteers participated in an interview that provided information regarding the following variables: sex, age, education level of the person with the highest level of education in the house, and self-referred skin colour.
IRB: This study had the approval of the Committee on Ethics of Research on Human Beings of the University Hospital Cassiano Antonio de Moraes of the Federal University of Espírito Santo, under the insertion number CCAE 31417020.3.0000.5064 and the approval number 4.009.337.Randomization The samples were multiples of 40 because it was the number established for sampling in each one of the sectors, in 171 random selected sectors. Blinding not detected. Power Analysis not detected. Sex as a biological variable not detected. Table 2: Resources
Software and Algorithms Sentences Resources The statistical package used for data analysis was SPSS version 20.0 (IBM). SPSSsuggested: (SPSS, RRID:SCR_002865)Results from OddPub: We did not detect open data. We also did not detect open code. Researchers are encouraged to share open data when possible (see Nature blog).
Results from LimitationRecognizer: We detected the following sentences addressing limitations in the study:This study has several limitations. As any cross-sectional study, it is not possible to determine causality, as investigators did not measure events occurrence along time. Interviews served as the bases for data collection, giving room to information bias, particularly interviewer and memory biases. Selective survival, a type of selection bias, was possibly a consequence of the sampling procedure, as the selection included only individuals in the disease mild spectrum because of the hospital admission or death of those with the severe form of the clinical presentation. Furthermore, a sensitivity of the test lower than 90% may have enabled false-negative results, but, even in these cases, the low prevalence probably kept a high negative predictive value. The detection of a 2.1% prevalence of infected individuals in the first stage of this cross-sectional study is probably a consequence of the very early application of the mitigation measures by the State Health Department. Such measures included partial social isolation and closure of schools, malls, and gyms since the detection of the first few cases by the health care system in March, as well as sanitary barriers in the motorway highways. On the other hand, this low prevalence indicates an epidemic still in its beginning capable of spreading to a huge contingent of susceptible individuals and overload the health care facilities, at the cost of many human lives. In this sense, this is vital information for the health administ...
Results from TrialIdentifier: No clinical trial numbers were referenced.
Results from Barzooka: We did not find any issues relating to the usage of bar graphs.
Results from JetFighter: We did not find any issues relating to colormaps.
Results from rtransparent:- Thank you for including a conflict of interest statement. Authors are encouraged to include this statement when submitting to a journal.
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- No protocol registration statement was detected.
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